Franchi, I. A.

Gilmour, I.

Pearson, V. K.

Wilson, R. C.

Wright, I. P.

English

Open Research Online (The Open University)

Open Research OnlineThe Open University’s repository of research publicationsand other research outputsThe effect of atmospheric entry heating onmicrometeorite volatile compositionConference or Workshop ItemHow to cite:Wilson, R. C.; Pearson, V. K.; Franchi, I. A.; Wright, I. P. and Gilmour, I. (2006). The effect of atmosphericentry heating on micrometeorite volatile composition. In: 69th Annual Meeting of the Meteoritical Society, 6-11 Aug2006, Zurich, Switzerland.For guidance on citations see FAQs.c© [not recorded]Version: [not recorded]Link(s) to article on publisher’s website:http://www.lpi.usra.edu/meetings/metsoc2006/pdf/5207.pdfCopyright and Moral Rights for the articles on this site are retained by the individual authors and/or other copyrightowners. For more information on Open Research Online’s data policy on reuse of materials please consult the policiespage.oro.open.ac.ukTHE EFFECT OF ATMOSPHERIC ENTRY HEATING ON MICROMETEORITE VOLATILE COMPOSITION.  R. C. Wilson, V. K. Pearson, I. A. Franchi, I. P. Wright and I. Gilmour. Planetary and Space Sciences Research Institute, Open University, Milton Keynes, UK. E-mail: r.c.wilson@open.ac.uk.   Introduction: With estimates of present day mass flux of   40,000 ± 20,000 t/yr [1], micrometeorites (MMs) may have served as a substantial contributor of volatiles and biologically significant molecules to the early Earth (or other young planetary surfaces).  These particles have high relative velocities, which dissipate their energy during atmospheric entry.  This study    investigates the effect of heating during atmospheric entry, on the survival and modification of organic material in MMs, and their involvement in pre-biotic organic chemistry.   Experimental Techniques: Due to the micrometer-sized   nature of MMs and their low availability for analysis,              compositionally analogous materials are required to represent unmelted MM particles.  In this case, 9mg aliquots of the      powdered carbonaceous chondrite Murchison are used.   The samples were heated in air to peak temperatures between 400 and 1000oC for the short durations of 5, 10 and 20 seconds, using a platinum filament fitted to a CDS 1000 pyroprobe. A thermocouple was embedded in the sample to quantify the peak temperature experienced by the sample.  The heating range is comparable to the peak temperatures experienced by unmelted MMs [2, 3].  Fractions of the heated sample were examined using elemental and thermo-gravimetric (TG) analysers, to assess the percentage carbon loss and volatile and organic survival. Results:  Elemental analysis demonstrates that the shorter the heating duration, the higher the percentage of total carbon        surviving any peak entry heating temperature.  A minimum of 5% total carbon remains in samples heated to ~900oC for 20s,       corresponding to carbonate minerals.  A minimum of 30% total carbon remains in samples heated to a similar peak temperature for 5s.  The remaining carbon is dominated by carbonate miner-als with detectable quantities of organics.   A greater abundance and broader range of organic material survives in samples exposed to higher entry heating temperatures at shorter heating durations. As TG CO2 profile peaks             corresponding to organics are very broad, it is not possible to identify individual organic components.  Alternative techniques are required to determine the nature of surviving organic         material.   Similarly, at shorter heating durations, a greater abundance of adsorbed and structurally bound water was able to survive, when exposed to higher entry heating temperatures.  The struc-tural   water peaks are consistent with cronstedtite [4], a domi-nant   phyllosilicate present in Murchison [5]. Implications:  The results demonstrate that organic        molecules and other volatile components can withstand certain atmospheric entry heating conditions.  It is therefore plausible that micrometeorites may have made a contribution to the or-ganic inventory of the early Earth, prior to the evolution of life. References: [1] Love, S. G. and Brownlee, D. E. 1993. Science 262:550-553. [2] Toppani, A. et al. 2001. Meteoritics and Planetary Science 36:1377-1396. [3] Love, S. G. and Brownlee, D. E. 1991. Icarus 89:26-43. [4] Morris, A. A. et al. 2005. Abstract #1925. 36th Annual Lunar and Planetary Science Conference [5] Buseck, P. R. and Hua, X. 1993. Annual Review of Earth and Planetary Sciences 21:255-305. 69th Annual Meteoritical Society Meeting (2006) 5207.pdf

The effect of atmospheric entry heating on micrometeorite volatile composition

http://oro.open.ac.uk/8153/1/The_Effect_of_Atmospheric_Entry_Heating_on_Micrometeorite_Volatile_Composition.pdf

The effect of atmospheric entry heating on micrometeorite volatile composition

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